Electrolytic water oxidation to dioxygen is a key challenge in the conversion of electricity to chemical fuels. This has been emphasized as part of electrochemical water splitting to make hydrogen (H2). From a more general perspective, there is a growing need to convert electrical energy from renewable sources to stored chemical energy in the form of fuels. Fuels are reductants, so a clean and abundant source of electrons is required to make them. Water is the most logical source of those electrons because of its abundance and the benign nature of the by-product, O2.
Water oxidation has become a very active area of research in recent years, inspired by energy challenges and by the emerging understanding of photosystem II. Metallic platinum and oxides/hydroxides of iridium, ruthenium, nickel, and other metals have long been used as anodes for this reaction, and recent discoveries of cobalt/phosphate and related catalysts have generated much interest. A variety of homogeneous catalysts and electrocatalysts for water oxidation have recently been reported, with a focus on Ru complexes but also including Ir, Mn, Co, and Fe compounds.
Despite the growing body of work on water oxidation catalysis, many substantial challenges remain in the development of an industrially viable catalyst, most notably cost, durability, and overpotential. Therefore, the discovery of a well-understood catalyst, particularly one based on inexpensive materials would be a significant advance.